When \(1<\lambda <1/c^2\)  we can still use this representation, after a change of variables which we now explain. As in [1]}, the curve with parameter \(\lambda \)  is isomorphic to the one with parameter \(\lambda ^{\prime }:=1/\lambda \)  under the isomorphism
\(X^{\prime }=X^{-1}\) , \(Y^{\prime }=Y(X^2\sqrt{\lambda })^{-1}\) , in the sense that the dashed coordinates satisfy the equation with the dashed parameter if the former satisfy (REF ).
